The present invention relates to a strip for manufacturing a ring-shaped electromagnetic element for an electrical machine.
German publication DE 26 29 532 C2 discloses a method of manufacturing a ring-shaped element out of electromagnetic material in which a strip is rolled up to form a ring for forming a stator or rotor of an electrical machine.
German publication DE 196 33 399 A1 discloses a strip for manufacturing a ring-shaped element of an electrical machine. The strip consists of segments which are separate from one another and together form the effective area of the element. Adjacent segments are directly connected to one another in each case by a web.
The object of this invention is to specify a strip with which the production of ring-shaped electromagnetic elements for electrical machines is simplified.
This object is achieved in a strip of the general type mentioned. The strip according to the invention is formed from segments which are separate from one another and together form the effective area of the element. Adjacent segments are directly connected in each case by a web. The web is integrally formed on the outside of the element. The web is formed in such a way that it absorbs an elastic deformation during the bending of the strip, whereas the segments remain essentially free of elastic deformation.
The special advantage is that this web, during the forming of the strip from an essentially elongated state to a ring shape, leads to a situation in which an essentially continuous, positive-locking connection of the segments can form at their respective butt joints. The butt joints in the formed ring-shaped electromagnetic element are formed so effectively that at most a minimum air gap is left. This air gap entails virtually no electromagnetic losses.
During bending, the preferred geometry and arrangement of the web provides for the edges to come into contact along the forming butt joint between the regions and for these edges to also remain in contact in a largely positive-locking manner. Otherwise, a situation may occur in which the edges certainly first come into contact during the bending of the strip, but regions of these edges become detached from one another during the further bending along the butt joint. The air gap forming in the process would greatly impair the functioning of the ring-shaped electromagnetic element in the electrical machine.
The strip is easy to manipulate and is robust and enables a rotor and/or stator to be manufactured with optimum use of material, for instance during the stamping of the strip. Cost-effective manufacture of rotor and/or stator parts of an electrical machine thus becomes possible.
Furthermore, the special shaping of the web prevents arching of the web during the bending, so that the strip has a flat electromagnetic effective area. Such rotors and/or stators manufactured by means of the strip exhibit virtually no losses due to the butt joints, so that such components may also be used for heavy-duty machines, in which, for instance, the stator is acted upon by a high magnetic field in which the electromagnetic effective area is saturated. Any mechanical stresses in the strip material are also prevented from affecting the electromagnetic properties of the strip, since the web absorbs the mechanical deformations. Although the web itself can carry magnetic flux, in the design per se it is preferably not part of the actual electromagnetic effective area of the ring-shaped electromagnetic element which is formed with the strip.
In a further preferred embodiment, the strip is provided with toothing at least on one side, this toothing preferably being provided as rotor and/or stator teeth. In a preferred embodiment in which the strip is bent to form a stator, an electric coil of coil wire is wound around stator teeth in the elongated strip, the cross-sectional shape of the coil wire being varied during the winding. Advantageous utilization of the space between the stator teeth is thus possible. Since this may be effected before the forming of the strip, mechanized manufacture and attachment of the coil or the coils are possible, since the stator teeth at this point in time are freely accessible.
In a further favourable embodiment, the outside diameter of the coil, during the winding of the coil about the stator tooth, is varied in such a way that the largest outside diameter of the coil is formed at the subsequent slot root. The coil is thus already largely preformed in such a way as would correspond to its final shape after the bending. Further advantageous utilization of the space between the stator teeth is thus possible. Both the wire cross section and the diameter of the coil may be varied during the winding of the coil.
Further advantages and refinements of the invention follow from the claims and the description.